Hydrodynamic Analysis od Wave Energy Converters with Different Motion Characteristics (WAVE CONVERTERS

Duration: 01.04.2010-31.03.2013 (36 months)

Coordination: Instituto Superior Técnico

Funding Entity: Portuguese Foundation for Science and Technology

The ocean waves are the result of the concentration of energy from various natural sources like sun, wind, tides, ocean currents, moon, and the rotation of earth. Thus, the ocean waves contain the highest concentration of renewable energy. The extraction of energy from ocean waves has received considerable attention throughout the world in the wake of increasing demand for power. The development of technologies to successfully harness the wave energy are based on different operational concepts, which can be divided into two major categories of wave energy converters (WECs): One is the active devices, where the interface element responds to the wave action and produces the mechanical work and the other is passive, which remains stationary and the water movement relative to the structure is made to work. The first category includes different types of floating bodies, whilst the second one includes structures fixed rigidly to the sea bottom or shore such as oscillating water column or overtopping channels (Vantorre et al. (2004)). In the proposed project, the study will focus on the hydrodynamic interactions of ocean waves with floating structures of different motion characteristics suitable for the design of wave energy devices. The principle motions of the floating body for the extraction of substantial wave energy are heave, pitch and roll. The energy is extracted from the relative motion of the bodies by using typical hydraulic systems to compress oil, which is then used to drive a generator. The present analysis will deal with the heaving and rolling motion of the device for different geometrical shapes. The basic mathematical model will be based on the boundary integral equation method (BIEM). Analytical tools already developed based on the Fourier transform technique will be utilized to study the devices of regular geometrical shapes. The study will be generalized to account for devices having arbitrary shapes and numerical tools will be developed based on BIEM. The optimization of the wave energy extraction largely depends on the control of power take-off system (Henderson (2006)). Therefore, the active control of the power take-off will increase the rate of power capture in various sea-states and in turn the longevity and economic viability of the project. The developed tool will also account for the power take-off efficiency and the power losses in valves. Further, the effect of different geometries on the efficiency of the device will be analyzed to choose the best possible configuration.

Project Team

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